This invention relates to a method and apparatus for interconnecting electrical circuit elements. More particularly, this invention relates to a new and improved solderless connector for establishing and maintaining electrical contact between circuit elements, while reducing or minimizing the change in impedance between the solderless connector body and the circuit devices which are to be connected therein.
A conventional method of interconnecting electrical or electronic circuit components consists of soldering terminals on the components to conductors which deliver current to or from the components. While generally suitable for its intended purposes, interconnecting electrical components via soldering terminals does suffer from certain drawbacks and deficiencies. For example, the substrate which supports an exposed terminal must be able to withstand relatively high temperatures with no adverse effects. Also, soldering connections can be time consuming and therefor be labor intensive and expensive. Another problem with soldered connections is the relative difficulty in disconnecting a soldered terminal during repairs and manufacturing.
In some applications it has been found desirable to replace soldering as a technique for use in establishing connections to flexible and other circuits. In these applications, the requisite electrical contact may be established by mechanically pressing the terminal portions of the circuit against terminal pads on the connector, device or another circuit. Such prior art pressure connections are customarily made with the aid of a solid resilient pressure applicator, such as an elastomeric member, which is placed in compression to bias at least one of the components to be electrically interconnected toward the other component to hold the terminal portions thereof in electrical contact. Such a solderless connection system is disclosed in U.S. Pat. No. 4,468,074, assigned to the assignee hereof and incorporated herein by reference.
While pressure connections of the type briefly described above facilitate circuit assembly and repair, and also allow for the use of low cost and low temperature plastics while eliminating the time consuming and thus costly step of soldering, the prior art pressure connectors have certain drawbacks and problems. For example, in high frequency electrical circuits, a sudden change or discontinuity in impedance can cause unwanted signal reflections. Such a condition may exist if two portions of a circuit, each portion having different characteristic impedances, are joined together. This impedance mismatch often arises from differences in dielectric constant of the connector materials as compared to the surroundings of the circuit elements outside of the connector. Thus, for example, two flexible circuits connected without solder by pressing together the conductors using a compressed elastomeric element (as described above) are subject to the change in surrounding dielectric constant caused when the flexible circuit leaves an environment of air and enters the connector.